Automatic torque controller



May 29, 1956 R. J. WEESNER ETAL 2,7

AUTOMATIC TORQUE CONTROLLER 3 Sheets-Sheer.

Filed June 19, 1953 m V/ 5 F mm I. 7 0 mm z E 6 W 9 May 29, 1956 WEESNER EI'AL 2,748,299

AUTOMATIC TORQUE CONTROLLER 3 Sheets-Sheet Filed June 19, 1953 L4 flu ll mfl l W5 E w m L M May 29, 1956 w s ETAL 2,748,299

AUTOMATIC TORQUE CONTROLLER Filed June 19, 1955 3 Sheets-Sheet 3 United States atent O AUTOMATIC onoun CONTROLLER Robert J. Weesner and Herbert L. Kelley, Milwaukee,

Wis., assignors to The Louis Allis Company, Milwaukee, Wis., a corporation of Wisconsin Application June 19, 1953, Serial No. 362,734 2 Claims. (Cl. 310-95) This invention relates generally to torque controlling devices and has as its purpose to provide an automatic torque controller by which the tension upon web or strand material being wound upon or unwound from a reel can be held uniform within reasonable limits despite a fixed rate of linear travel for the web or strand material and the changing diameter of the coil or roll on the reel.

Heret'ofore control systems for this purpose have generally required costly and rather unreliable booster generators or regulators since they usually operated upon the principle of regulating the field current of the motor driving the reel. Patent No. 2,451,901, issued October 21, 1948, to B. J. Auburn is an example of such past control systems.

In comparison the device of this invention is relatively inexpensive and trouble-free in operation by virtue of the fact that it achieves its purpose by the simple expedient of properly coordinating the torque transmitting ability of an electromagnetic coupling with the speed of the reel, the coupling being connected between the reel and its motor in cases where the strand material is being wound up and between the reel and a fixed anchor where the material is being unwound.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes inthe precise embodiment of the hereindisclosed invention may be made as come Within the scope of the claims.

The accompanying drawings illustrate several complete examples of thephysical embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a diagrammatic view illustrating one adaptation of this invention to a reel upon which the web or strand material is being wound;

Figure 2 is a diagrammatic view illustrating a modification of this adaptation of the invention;

Figure 3 is a diagrammatic view illustrating another adaptation of this invention; and

Figure 4 is a diagrammatic view of an adaptation of this invention to the control of web tension where the material is being unwound from the reel.

Referring now particularly to the accompanying drawings and especially to Figures 1, 2 and 3, the numeral 5 designates a reel upon which web or strand material 6 is to be wound. The reel is driven by any suitable prime mover, such as a motor 7, having an output shaft 8 running at a substantially uniform speed drivingly connected to the reel through a magnetic coupling 9.

The Web or strand material 6 is fed to the reel at a uniform rate of linear travel by the machine or apparatus designated generally by the numeral 10, and which may e a tel mill, a oa ng mach ne p i t g was. eage m kin ma h n or a .so-salled s ash r hich enemies 2,748,299 Patented May 29, 1956 upon a web composed of a plurality of separate adjacent strands. In all such machines the web or strand material travels at a uniform linear speed and in all instances it is desirable and often imperative that the web or strand material be maintained under a uniform degree of tension.

Since the tension maintained upon the web or strand material by the driven reel would vary with the instantaneous diameter of the coil or roll being wound upon the reel in the absence of some means for continuously increasing the torque transmitted to the reel as the diam-v eter of its coil or roll increases, and since, of course, the speed of the reel must diminish as the diameter of the coil or roll increases, some means must be provided to continually increase the torque delivered to the reel as its speed of rotation decreases.

This objective is accomplished in a very simple and direct manner by this invention, and the key to the solution of the problem lies in the impositive driving connection between the reel and its driving motor '7 provided by the magnetic coupling 9, and in keeping the excitation of the coil 11 of this electromagnetic coupling inversely pro: portional to the speed of rotation of the reel. This arrangement permits the speed of the reel to be determined solely by the rate of delivery of web or strand material to the reel and the surface diameter of the coil or roll thereon at any instant. This may be done in different ways.

In that embodiment of the invention illustrated in Figure 1, the desired proportional excitation of the electromagnet is obtained through the use of a frequency convert'er 12 the rotary element 13 of which is drivingly connected to the reel 5' either directly as shown or indirectly but, in any event, so that the speed of its rotation is always proportional to the speed of rotation of the reel 5. The primary windings of the frequency converter are energized from a three-phase power line 14 and the direction of rotation of the resulting flux is the same as that in whic'nthe rotary element 13 is driven by the reel.

Accordingly, the voltage across the terminals 15 and 16 of the secondary windings of the converter, which may be either single-phase or three-phase, is zero when the speed of the rotor equals the speed of the rotating field established by the three-phase A. C. power source, i. e., at synchronous speed, and X volts (depending upon the transformation ratio) at zero speed. The voltage across the terminals 15 and 16 thus varies inversely with the speed of the reel 5, but since this is an A. C. voltage and the coil 11 is to be energized by direct current, a rectifier bridge network 17 is interposed in the circuit connecting the output terminals 15 and 16 with the coil.

It is, or course, understood that the speed of the motor 7 is suflicient to drive the reel at the maximum speed required and that the voltage delivered by the frequency converter and with which the coil 11 is excited is such as to produce just the right degree of attraction across the air gap of the driving and driven elements of the magnetic coupling necessary to maintain the desired tension upon the web or strand material 6.

In that form of the invention illustrated in Figure 2 the coil 11 of the magnetic coupling is energized or excited by voltage derived from a tachometer generator 18 and a source of fixed excitation voltage shown in this instance as a battery 19. The rotary element of the tachometer generator is drivingly connected either directly or indirectly to the reel 5; and as shown, these two voltage sources are connected in series across the coil 11 and in opposing polarity so that their voltages are algebraically added. Accordingly, as the speed of rotation of the reel, and consequently the rotary element 18 of the tachometer generator, decreases the net volta ap ear n across the sai 11 nc e ses to h r y correspondingly increase the torque delivered from the driving to the driven element of the magnetic coupling 9.

It is, of course, understood that the voltage derived by the fixed source 19 and from the tachometer generator must be properly coordinated and of a magnitude to effect excitation of the coil 11 as required to bring about the desired increase in torque transmission.

In the Figure 2 embodiment of the invention the volt age delivered by the tachometer generator is used directly to control the excitation of the electromagnet and hence the generator must be capable of delivering relatively large power. It is also possible to use the tachometer generator merely as a control for an electronic D. C. power supply in which case it can be much smaller since it then functions merely as a pilot generator. One such adaptation of the'invention is illustrated in Figure 3.

Ashere shown the coil 11 of the electromagnet is connected across the secondary of a transformer 20 in series-circuit with the plate and cathode of a gas-illed grid controlled rectifier tube 21 of the thyratron type. A back rectifier 22, either a diode tube or of the selenium type, is shunted across the coil 11 so that it opposes cur rent flow through the rectifier 22 during the intervals of time that the thyratron rectifier tube Zll is conducting current to the coil ll. Because an electromagnet like coil 11 is highly inductive, there is a tendency for the current in coil 11 to continue to flow and for the flux induced by the current to continue in existence after tube 21 ceases to conduct. Since the current tends to continue flowing in the same direction in coil 11, the rectifier 22 provides a relatively low resistance path in series with the coil which further prolongs the fiow of current therethrough. In this embodiment of the invention, therefore, the back rectifier 22 cooperates with the thyratron rectifier 21 to insure a substantially continuous fiow of current in coil 11 and, therefore, insure a minimum of flux pulsation in the electromagnet.

The conductivity of the tube 21 is governed by the output of a pilot tachometer generator 23 the rotary element of which is connected with the reel to turn therewith. The output of this pilot tachometer-generator is fed to a rectifier bridge circuit 24 and from there is impressed upon the resistance element of a potentiometer 25 by which the level of the tension control may be adjusted.

It is, of course, understood that to have the tube 21 fire at the proper time, as determined by the adjustment of the potentiometer 25, the bias upon the grid of the tube must be properly coordinated with the tension level adjustment as determined by the setting of the potentiometer 25. To this end a suitable phase shifting network 27 is provided which includes a manually adjustable control 28. Since such phase shifting networks and the control of thyratron type rectifiers is well known in the art, further description thereof is unnecessary; the important consideration being that, in the Figure 3 embodiment of the invention, the constant voltage derived from the battery 26 (or other suitable source of D. C.) is algebraically added to a voltage EC which is always proportional to the speed of the reel, and the sum of the two designated E is used to control the tube 21 which in turn governs the excitation of the electromagnet. Accordingly the excitation of the electromagnet is always inversely proportional to the speed of the reel.

Where the material is to be unwound from the reel, as is the case in the embodiment of the invention shown in Figure 4, there is, of course, no need to drive the reel, but instead its rotation brought about by withdrawing the web or strand material therefrom must be properly braked to maintain the desired uniform tension on the material. Hence, in lieu of the reel motor or prime mover of the previous embodiments of the invention, one element 9' of the magnetic coupling is secured against turning. In all other respects the controller may be as shown in Figure l or Figure 2, the former scheme being the one chosen for illustration.

Though three different means have been illustrated to produce the required excitation or energization of the coil 11 of the magnetic coupling, it will be evident that in each instance this means includes a dynamo electric machine having a rotating element drivingly connected with the reel, and it will be understood that where the term dynamo electric machine is employed in the claims it is to be interpreted as covering units such as the frequency converter 12, the tachometer-generators 18 and 23 and all equivalent machines capable of delivering either directly or in association with other voltage sources an excitation voltage which varies inversely with the speed of rotation of its rotary element and consequently the reel to which the rotary element is drivingly connected, or as in Figure 3 capable of delivering a control voltage which is used to govern an electronic D. C. power supply by which an excitation voltage inversely proportioned to the speed of rotation of the reel is delivered to the electromagnet.

It should also be understood that while one element of the magnetic coupling is positively connected with a prime cover-the reel motor 7where the material is being wound upon the reel, and this same element of the coupling is secured against turning where the apparatus controls the tension on material being unwound, in each instance this element of the coupling has a uniform R. P. M. In the latter case it is zero and in the former it is fast enough to turn the reel at the maximum speed required.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in this art that this invention provides an extremely simple, inexpensive and reliable torque control system which, though especially adapted for maintaining uniform tension upon web or strand material being wound upon a reel, is also useful for maintaining uniform tension upon such material as it is unwound from a reel at a uniform rate of linear travel.

What we claim as our invention is:

1. An automatic torque control system for maintaining substantially uniform tension on a web or strand being wound onto or unwound from a reel at some predetermined substantially uniform rate of linear travel, comprising: an electromagnetic coupling having complementary elements with an air gap therebetween, and having a winding for producing a magnetic attraction between said elements to render said coupling capable of transmitting a torque which varies with the strength of the magnetic attraction across the air gap; means for positively drivingly connecting one of the elements of the magnetic coupling with the reel so that it turns therewith; means connected with the other element of the coupling for constraining it to a predetermined substantially uniform R. P. M.; the impositive torque transmitting connection between the elements of the coupling enabling the speed of the reel to be determined by the rate of linear travel of the web or strand and the diameter of the coil on the reel at any instant; a frequency converter having primary and secondary windings, output terminals for the secondary windings, and a rotor; means drivingly connecting the rotor of the frequency converted with the reel so that the rotor turns at a speed proportional to that of the reel; means connecting the primary windings of the frequency converter to a source of electrical power to produce a flux which rotates in the direction of rotor rotation so that the voltage across the output terminals of the secondary windings varies inversely with the speed of the reel; means connected with the output terminals of the secondary windings for rectifying the A. C. output of the frequency converter; and means for impressing the rectified output of the frequency converter across the ends of the winding of the electromagnetic coupling whereby the coupling winding is excited with a voltage which is inversely proportional to the speed of the reel, so that the torque transmitted by the coupling increases as the speed of the reel decreases.

2. An automatic speed and torque control system for 'iaintaining substantially uniform tension on a Web or strand being wound upon a reel at some predetermined substantially uniform rate of linear travel, comprising: a prime mover having a power takeoff shaft revolving at some predetermined substantially uniform speed; an electromagnetic coupling having driving and driven elements arranged with an air gap therebetwecn and having a winding for producing a magnetic attraction between said driving and driven elements to render said coupling capable of transmitting a torque which varies with the strength of the magnetic attraction across the air gap; means for positively drivingly connecting the driving ele ment of the magnetic coupling with the power takeoil shat t of the prime mover; means for positively connecting the driven element of the coupling with the reel, the impositive driving connection thus established between the prime mover and the reel enabling the speed of the reel to be determined by the rate of delivery of the web or strand to the reel and the diameter of the coil on the reel at any instant; a frequency converter having primary and secondary windings, output terminals for the secondary windings, and a rotor; means drivingly connecting the rotor of the frequency converter with the reel so that the rotor turns at a speed proportional to that of the reel; means connecting the primary windings of the frequency converter to a source of electrical power to produce a flux which rotates in the direction of rotor rotation so that the voltage across the output terminals of the secondary windings varies inversely with the speed of the reel; means connected with the output terminals of the secondary windings for rectifying the A C. output of the frequency converter; and means for impressing the rectified output of the frequency converter across the ends of the winding of the electromagnetic coupling whereby the coupling winding is excited with a voltage which is inversely proportional to the speed of the reel, so that the torque transmitted by the coupling increases as the speed of the reel decreases.

References Cited in the file of this patent UNITED STATES PATENTS 2,357,201 Hornbostel Aug. 29, 194-4 2,469,706 Winther May 10, 1949 2,541,182 Winthcr Feb. 13, 1951 FOREIGN PATENTS 544,941 Great Britain May 4, 1942 

